It is mechanism refers to when separate parts of a website are treated differently in terms of SEO.
A search engine spider will, in theory, focus more heavily on the main content block toward the center of the page than a footer, a navigation menu, or advertisements or calculate the importance or relevance of a page to the web.

Page segmentation is a study technique devised by search engines to calculate the importance or relevance of a page to the web. Noise levels are calculated based on the amount of information contained in a website.

Page segmentation is all about to track the site visitors like which are the landing pages and exit pages. So that you can have a brief idea that how can you improve exit pages content and design to make it more convenient for the landing user.

Page segmentation is the process by which a scanned page is divided into columns and blocks which are then classified as halftones, graphics, or text. Past techniques have used the fact that such parts form right rectangles for most printed material.